.functions

local w,h = term.getSize()

--Center Text

function printCentered (y,s)
    local x = math.floor((w - string.len(s)) /2)
    term.setCursorPos(x,y)
    term.clearLine()
    term.write(s)
end

--Drawmenu

local nOption = 1

local function drawMenu()
    term.setBackgroundColor(colors.cyan)
    term.clear()
    term.setCursorPos(1,1)
    local logo = paintutils.loadImage("os/.logo")
    paintutils.drawImage(logo, 1, 1)
    term.setBackgroundColor(colors.cyan)

    term.setCursorPos(w-11,1)
    if nOption == 1 then
        term.write("DOS")
    elseif nOption == 2 then
        term.write("EXECUTIVE")
    elseif nOption == 3 then
        term.write("SHUTDOWN")
    elseif nOption == 4 then
        term.write("DISK")
    else
        end
end

--GUI

term.clear()
local function drawFrontend()
    printCentered(math.floor(h/2) -3, "")
    printCentered(math.floor(h/2) -2, "START")
    printCentered(math.floor(h/2) -1, "")
    printCentered(math.floor(h/2) + 0, (nOption == 1 and "[ DOS ]") or "DOS")
    printCentered(math.floor(h/2) + 1, (nOption == 2 and "[ EXECUTIVE ]") or "EXECUTIVE")
    printCentered(math.floor(h/2) + 2, (nOption == 3 and "[ SHUTDOWN ]") or "SHUTDOWN")
    printCentered(math.floor(h/2) + 3, (nOption == 4 and "[ DISK ]") or "DISK")
end

--Display

drawMenu()
drawFrontend()

while true do
    local e,p = os.pullEvent()
        if e == "key" then
            local key = p
            if key == 17 or key == 200 then

                if nOption > 1 then
                    nOption = nOption -1
                    drawMenu()
                    drawFrontend()
                end
            elseif key == 31 or key == 208 then
                if nOption < 4 then
                    nOption = nOption +1
                    drawMenu()
                    drawFrontend()
                end
        elseif key == 28 then
            break
end
end
end

term.clear()

--Conditions
if nOption == 1 then
    term.setBackgroundColor(colors.black)
    shell.run("os/.DOS")
elseif nOption == 2 then
    shell.run("os/.EXECUTIVE")
elseif nOption == 3 then
    shell.run("os/.SHUTDOWN")
else
    term.setBackgroundColor(colors.black)
    term.clear()
    term.setCursorPos(1,1)
    print("You are now in DOS mode. Write 'back' to return to interface")
    print("---------------------------------------------------")
    shell.run("chkdisk")
end